4 files changed, 27 insertions, 12 deletions

diff --git a/src/cmd/cgo/ast.go b/src/cmd/cgo/ast.go
index 29fe55240..9b122676c 100644
--- a/src/cmd/cgo/ast.go
+++ b/src/cmd/cgo/ast.go
@@ -35,6 +35,7 @@ type Prog struct {
 	Typedef map[string]ast.Expr;
 	Vardef map[string]*Type;
 	Funcdef map[string]*FuncType;
+	PtrSize int64;
 }
 
 // A Type collects information about a type in both the C and Go worlds.
diff --git a/src/cmd/cgo/gcc.go b/src/cmd/cgo/gcc.go
index 27090fdf4..e3f526845 100644
--- a/src/cmd/cgo/gcc.go
+++ b/src/cmd/cgo/gcc.go
@@ -20,7 +20,7 @@ import (
 	"strings";
 )
 
-func (p *Prog) loadDebugInfo(ptrSize int64) {
+func (p *Prog) loadDebugInfo() {
 	// Construct a slice of unique names from p.Crefs.
 	m := make(map[string]int);
 	for _, c := range p.Crefs {
@@ -57,7 +57,7 @@ func (p *Prog) loadDebugInfo(ptrSize int64) {
 	b.WriteString("}\n");
 
 	kind := make(map[string]string);
-	_, stderr := gccDebug(b.Bytes());
+	_, stderr := p.gccDebug(b.Bytes());
 	if stderr == "" {
 		fatal("gcc produced no output");
 	}
@@ -109,7 +109,7 @@ func (p *Prog) loadDebugInfo(ptrSize int64) {
 	for i, n := range names {
 		fmt.Fprintf(&b, "typeof(%s) *__cgo__%d;\n", n, i);
 	}
-	d, stderr := gccDebug(b.Bytes());
+	d, stderr := p.gccDebug(b.Bytes());
 	if d == nil {
 		fatal("gcc failed:\n%s\non input:\n%s", stderr, b.Bytes());
 	}
@@ -158,7 +158,7 @@ func (p *Prog) loadDebugInfo(ptrSize int64) {
 
 	// Record types and typedef information in Crefs.
 	var conv typeConv;
-	conv.Init(ptrSize);
+	conv.Init(p.PtrSize);
 	for _, c := range p.Crefs {
 		i := m[c.Name];
 		c.TypeName = kind[c.Name] == "type";
@@ -175,9 +175,9 @@ func (p *Prog) loadDebugInfo(ptrSize int64) {
 // gccDebug runs gcc -gdwarf-2 over the C program stdin and
 // returns the corresponding DWARF data and any messages
 // printed to standard error.
-func gccDebug(stdin []byte) (*dwarf.Data, string) {
+func (p *Prog) gccDebug(stdin []byte) (*dwarf.Data, string) {
 	machine := "-m32";
-	if os.Getenv("GOARCH") == "amd64" {
+	if p.PtrSize == 8 {
 		machine = "-m64";
 	}
 
diff --git a/src/cmd/cgo/main.go b/src/cmd/cgo/main.go
index 0832b3f40..b629f0a22 100644
--- a/src/cmd/cgo/main.go
+++ b/src/cmd/cgo/main.go
@@ -22,20 +22,34 @@ func usage() {
 	flag.PrintDefaults();
 }
 
-const ptrSize = 8	// TODO
+var ptrSizeMap = map[string]int64 {
+	"386": 4,
+	"amd64": 8,
+	"arm": 4
+}
 
 func main() {
 	flag.Usage = usage;
 	flag.Parse();
 
+	arch := os.Getenv("GOARCH");
+	if arch == "" {
+		fatal("$GOARCH is not set");
+	}
+	ptrSize, ok := ptrSizeMap[arch];
+	if !ok {
+		fatal("unknown architecture %s", arch);
+	}
+
 	args := flag.Args();
 	if len(args) != 1 {
 		usage();
 		os.Exit(2);
 	}
 	p := openProg(args[0]);
+	p.PtrSize = ptrSize;
 	p.Preamble = p.Preamble + "\n" + builtinProlog;
-	p.loadDebugInfo(ptrSize);
+	p.loadDebugInfo();
 	p.Vardef = make(map[string]*Type);
 	p.Funcdef = make(map[string]*FuncType);
 
diff --git a/src/cmd/cgo/out.go b/src/cmd/cgo/out.go
index 36fbe0349..91473abeb 100644
--- a/src/cmd/cgo/out.go
+++ b/src/cmd/cgo/out.go
@@ -100,8 +100,8 @@ func (p *Prog) writeOutput(srcfile string) {
 			structType += fmt.Sprintf("\t\t%s p%d;\n", t.C, i);
 			off += t.Size;
 		}
-		if off%ptrSize != 0 {
-			pad := ptrSize - off%ptrSize;
+		if off%p.PtrSize != 0 {
+			pad := p.PtrSize - off%p.PtrSize;
 			structType += fmt.Sprintf("\t\tchar __pad%d[%d];\n", npad, pad);
 			off += pad;
 			npad++;
@@ -116,8 +116,8 @@ func (p *Prog) writeOutput(srcfile string) {
 			structType += fmt.Sprintf("\t\t%s r;\n", t.C);
 			off += t.Size;
 		}
-		if off%ptrSize != 0 {
-			pad := ptrSize - off%ptrSize;
+		if off%p.PtrSize != 0 {
+			pad := p.PtrSize - off%p.PtrSize;
 			structType += fmt.Sprintf("\t\tchar __pad%d[%d];\n", npad, pad);
 			off += pad;
 			npad++;